1. Field of the Invention
This invention relates to an access device for a digital network such as a digital service unit (DSU).
2. Background of the Invention
The term Digital Service Unit (DSU), as used herein, may in general also embrace combined Digital Service Unit/Customer Service Units (CSU), CSU's, or similar digital network access devices as will be appreciated by those skilled in the art.
In order to achieve higher reliability in data communications at higher speed, many users are converting to all digital networks such as digital data systems (DDS) networks. There are three distinctive services in the DDS network: (i) Basic DDS (also called Standard DDS or DDS I), (ii) DDS-SC (also called DDS II) and (iii) CC64 (also called CC64k Clear), with the first two services including a plurality of line rates. Detailed technical information regarding the various DDS services may be obtained in the various technical specifications published by AT&T and other digital service providers for their digital data systems (e.g. AT&T Communications Technical Reference PUB 62120, 1984).
Typically, in prior DSU designs of the assignee of the present invention, the user/customer needed to manually strap the DSU units to reflect the proper DDS rate/service, such need requiring an experienced person to install the DDS units.
In U.S. Pat. No. 4,745,601 to the assignee of the present invention, in column 8, line 18, it is stated that the service and line rate may be automatically derived from the DDS data stream. Additionally, a number of companies have commercially released DSU units that provide automatic detection of the line rate and service on the DDS network. Hence, automatically detecting the proper DDS rate/service has been implemented in a number of products forming part of the prior art.